In an excellent example of how chemistry and archaeology run hand to hand, Thomas Fenn a graduate student from in anthropology at the University of Arizona, Tucson has sampled isotopes from copper jewelery of sub-Saharan Africa,

“three of which result from the slow decay of radioactive elements such as uranium. Fenn used the relative quantities of these to date the copper ore used to make the items, and distinguish one source of copper from another. “

His results show that the ingots from sub-Saharan Africa have shown a signature of copper ore from Morocco. This strongly suggests that trans-Saharan trade began hundreds of years earlier than previously thought. Even more remarkably, Fenn began to find copper that was clearly from Morocco in items that archaeologists had dated to as far back at 400 AD! That means people we crossing one of the world’s largest deserts to trade copper, among other things. He presented his findings at the American Chemistry Society meeting on 26 March in Atlanta, Georgia.